History of Present Illness (HPI)

The patient is a 46-year-old female presenting with complaints of itching and a rash localized to the upper body. She reports that these symptoms have been ongoing for a few weeks. Initially, she was treated with a short course of prednisone for 5 days, which resulted in a reduction of itching. However, the symptoms have recurred. The patient also mentions a possible reaction to a medication delivered via a patch, which her primary care physician (PCP) has since discontinued. Additionally, she has been sleeping on a new mattress purchased from Amazon, which she suspects may contain allergens causing her symptoms.

Differential Diagnosis

Single Most Likely Diagnosis

• Contact Dermatitis: This is the most likely diagnosis given the patient's history of a new mattress and a possible reaction to a medication patch. Contact dermatitis is a type of inflammation of the skin that occurs when the skin comes into contact with an irritant or allergen, leading to symptoms such as itching, redness, and rash.

Other Likely Diagnoses

• Atopic Dermatitis (Eczema): Given the patient's history of itching and rash, and the initial response to prednisone, atopic dermatitis is a plausible diagnosis. This condition is characterized by chronic inflammation of the skin and is often associated with allergies and asthma.
• Allergic Reaction to Medication: Although the patient's PCP stopped the medication patch, an allergic reaction to another medication could still be considered, especially if the patient has started any new medications recently.
• Irritant Contact Dermatitis: This could be due to the new mattress or other environmental factors that the patient has been exposed to, causing irritation and inflammation of the skin.

Do Not Miss Diagnoses

• Bullous Pemphigoid: An autoimmune disease that can cause blistering of the skin and is more common in older adults. Although less likely, it's critical to consider due to its potential severity and the need for specific treatment.
• Drug Rash (including DRESS Syndrome): A potentially life-threatening condition that can occur in response to certain medications. It's essential to consider this diagnosis, especially given the patient's recent medication changes.
• Cutaneous T-Cell Lymphoma (Mycosis Fungoides): A rare type of skin cancer that can present with skin patches, plaques, or rashes, and is often mistaken for other dermatological conditions.

Rare Diagnoses

• Pityriasis Rosea: A skin condition characterized by a rash that can be triggered by viral infections or other factors. It's less likely given the patient's history but could be considered if other diagnoses are ruled out.
• Dyshidrotic Eczema: A type of eczema that primarily affects the hands and feet but can occasionally involve other areas, including the upper body. It's characterized by small, itchy blisters.